One Step Synthesis of a Highly Symmetrical Hexacyclic System from

One Step Synthesis of a Highly Symmetrical Hexacyclic System from a Simple Naphthol 

In an attempt to use phenolic Mannich bases in a synthesis of 3-chromanones, a mixture of 1 -[(dimethylamino)methyl]-2-naphthol and a-chloroacrylonitrile was heated under reflux in anhydrous dioxane. The product, however, which was formed in 55% yield, was shown to be the naphthonaphthopyranopyran 1. 

Treatment of the sulfoxide prepared from p-cresol and thionyl chloride with a mixture of TFAA and KHCO3 in acetonitrile at -30°C led to formation of an orthoquinone mono(monothioketal). Desulfurisation with NiCl2(PPh3)2 gave 2-(4-methylphenoxy)-4-methylphenol in 38% overall yield. 

Reaction of Jt-excessive heterocycles (e.g. thiophene, indole), enol ethers (e.g. dihydropyran) and enol acetates, and carboxylic acids with chlorosulfonyl isocyanate leads in generally excellent yields to A-chlorosulfonylamides. These intermediates are converted into the corresponding nitriles by heating in DMF, although the yields can be somewhat variable. A recent reinvestigation of the N-chlorosulfonylamide to nitrile conversion revealed that treatment of the amides with one equivalent of triethylamine led to formation of the nitriles in excellent yield. Clearly, the mechanisms of the DMF and the EtsN induced transformations are different. 

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